×

Automatic frequency offset compensation apparatus

  • US 5,561,665 A
  • Filed: 07/31/1995
  • Issued: 10/01/1996
  • Est. Priority Date: 08/11/1994
  • Status: Expired due to Term
First Claim
Patent Images

1. An automatic frequency compensation apparatus comprising:

  • first difference vector generation means for continuously generating at least a difference vector provided between first signals in two consecutive first symbol intervals of a quadrature baseband signal per said first symbol period, said quadrature baseband signal being provided through a non-synchronizing quadrature detection of a time-division-multiples digital modulation signal received and for normalizing said difference vector;

    second difference vector generation means for generating a predetermined difference vector provided between second signals in two consecutive second symbol intervals of a predetermined time-division multiplex frame synchronizing signal;

    vector correlation means responsive to said first and second difference vector generation means for providing a frame vector correlation signal indicative of a correlation between the normalized difference vector and said predetermined difference vector;

    comparing means for comparing said frame vector correlation signal with a predetermined value and generating a comparing result signal;

    counting means for counting said comparing result signal when said vector correlation is larger than said predetermined value;

    frequency offset prediction means responsive to said comparing result signal for predicting a frequency offset of an oscillation signal used for receiving said time-division-multiplex digital modulation signal from a center frequency of said time-division-multiples digital modulation signal in accordance with said normalized difference vector and said predetermined difference vector, renewing the predicted frequency offset using a convergent coefficient when said vector correlation is larger than said predetermined value, and decreasing said convergent coefficient with an increase in an output of said counting means; and

    frequency offset compensation means for rotating a phase of said baseband signal in accordance with the predicted frequency offset to output the frequency offset compensated baseband signal.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×